The circumstances under which deaf people learn sign language are highly heterogeneous. Among deaf signers are people who first acquired sign language either during or after early childhood and who began the task with either much or scant previous language experience. Are there long-range consequences of these unique circumstances on the ability to comprehend language? A series of six studies was designed to answer the question. Three goals guide the studies. The first goal is to replicate the finding that the age at which deaf signers acquire sign language affects their ability to process, comprehend and remember sentences in American Sign Language (ASL). The finding will be replicated by testing a new sample of deaf signers who range in age of sign language acquisition from birth to 13 years. The second goal is to test the hypothesis that age of acquisition exerts differential effects on first-and second-language acquisition. This will be accomplished by testing the sign language comprehension skills of four groups of signers, (1) native learners of ASL, (2) childhood and (3) adolescent first-language learners of ASL, and (4) native learners of English who learned ASL as a second language in adolescence. The third goal is to test the hypothesis that childhood language acquisition affects the automaticity with which words can be identified and remembered in terms of perceiving phonological shape and retrieving and remembering lexical meaning. This will be accomplished by comparing the four groups' skills on tasks of lexical processing, sentence comprehension, and narrative comprehension. The results will have direct relevance to the education of deaf children who often learn language after early childhood.